struct IHelloWorld : public IUnknown
{
public:
    // IUnknown
    STDMETHOD_(ULONG, AddRef)() PURE;
    STDMETHOD_(ULONG, Release)() PURE;
    STDMETHOD(QueryInterface)(REFIID riid, void** ppv) PURE;

    // IHelloWorld
    STDMETHOD(HelloWorld)(BSTR bsMessageText) PURE;
};

struct __declspec(uuid("{7D51904D-1645-4a8c-BDE0-0F4A44FC38C4}")) IHelloWorld;